A major determinant of the quality of life for elderly individuals is the efficiency of their mental processes. Loss of neurocognitive functioning has been noted in elderly individuals; the severity of this loss ranges from simple memory deficits to profound dementia of the Alzheimer's variety. It is important to discover to what extent such functional decline is preventable and reversible. Specific to this project is the possibility that nutritional factors are important. Since estimates of the incidence of micronutrient deficiency in the elderly is quite large, intervention could significantly reduce the public health burden. The aim of this multidisciplinary study is to determine the prevalence of elevated homocysteine, brain disease, and cognitive decline in the homebound elderly. From 7500 homebound elderly, representative of all registered cases from a specified geographical area, a cohort of 1600 elders will be assessed. The assessment will include dietary history and serum nutrient levels, as well as comprehensive neuropsychological testing. Clinical examination and MRI scans will be performed on a subset of 400 subjects. Known risks for cognitive impairment such as diagnosed depression, anxiety, hypertension, diabetes, atrial fibrillation, medications, APOE, saturated fat intake, and mutations of MTHFR will be measured and included in analyses as covariates and effect modifiers.